The present technology relates to an optical recording medium, a method of manufacturing the same, and a recording layer for an optical recording medium, and more particularly, to an optical recording medium including two or more recording layers.
Hitherto, a compact disc (CD), a digital versatile disc (DVD), a Blu-ray disc (BD, registered trademark), and the like have led the market of optical recording media. However, recently, along with 4K video, file base of video, and a rapid increase in data stored as cold data, a further increase in capacity has been demanded for an optical recording medium. To cope with this demand, a large-capacity optical recording medium corresponding to a double-sided recording layer such as an archival disc (AD) has appeared, and a market of a new large-capacity optical recording medium has been raised.
Examples of recordable optical recording medium includes a rewrite type optical recording medium represented by a compact disc-rewritable (CD-RW) and a digital versatile disc±rewritable (DVD±RW), and a write-once type optical recording medium represented by a compact disc-recordable (CD-R) and a digital versatile disc-recordable (DVD-R), and the latter has greatly contributed to expansion of a market as a cheap medium. Accordingly, even in a large-capacity optical recording medium corresponding to a blue laser, it is considered that a reduction in the cost of the write-once type optical recording medium is necessary to expand a market.
In addition, storage reliability of the optical recording medium is typically higher in comparison to a hard disk drive (HDD), a flash memory, and the like due to recording and reproduction principle thereof. For example, the optical recording medium begins to be used for storage of important information, and a demand as archival media has been increasing in recent years.
Examples of a recording material that can be used in the write-once type optical recording medium include an inorganic material and an organic pigment material.
In a write-once type optical recording medium of the related art, as the recording material, the organic pigment material has been mainly examined. However, in a recent large-capacity optical recording medium, as the recording material, the inorganic material has been widely examined (for example, refer to Patent Document 1 to Patent Document 3).
However, in recent, in a high-density optical recording medium such as a recordable DVD and a recordable BD, to further increase recording capacity, a technology of forming the recording layer as a multi-layer has been widely employed. In a multi-layer optical recording medium, recording and reproduction of an information signal with respect to a recording layer located on the deepest side from an information reading side are performed by using laser light that is transmitted through recording layers on a front side. Accordingly, as the number of recording layers increases, the number of recording layers through which the laser light is transmitted until reaching the recording layer located on the deepest side increases. Accordingly, recording layers other than the recording layer located on the deepest side from the information reading surface side are desired to have a high transmittance. In addition, a configuration in which a multi-layer film is disposed on both surfaces of a medium is also employed to increase the recording capacity. According to the double-sided configuration, capacity also increases approximately two times.
In the write-once type optical recording medium, a demand for multi-layering of the recording layer to increase recording capacity has increased, and to cope with the demand, an improvement of a transmittance of an inorganic recording layer becomes one important technology.